Thermoplastic elastomers having improved adhesive properties

ABSTRACT

Adhesive compositions comprising a thermoplastic elastomer and a block copolymer with rigid vinyl aromatic blocks and non-rigid blocks of dienes and vinyl aromatic monomers.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates generally to thermoplastic elastomer (TPE)materials. Thermoplastic elastomers are broadly defined as rubber-likematerials that, unlike conventional vulcanized rubbers, can be processedand recycled like thermoplastic materials, yet have properties andperformance similar to that of vulcanized rubber at servicetemperatures. The invention more specifically relates to thermoplasticelastomers which have been modified by the addition of a specific vinylaromatic block copolymer. The compositions of the invention haveimproved adhesive properties with respect to polymeric substrates, andparticularly with respect to engineering thermoplastics.

[0003] 2. Description of the Prior Art

[0004] Blends which have a combination of both thermoplastic and elasticproperties are generally obtained by combining a thermoplastic resinwith an elastomeric material in a way such that the elastomer isintimately and uniformly dispersed as a discrete particulate phasewithin a continuous phase of the thermoplastic. Early work with thevulcanization of the elastomer phase is found in U.S. Pat. No. 3,037,954which discloses static vulcanization, as well as dynamic vulcanizationwherein a vulcanizable elastomer is dispersed into a resinousthermoplastic polymer and the elastomer is cured (crosslinked) whilecontinuously mixing and shearing the blend.

[0005] U.S. Pat. No. 4,130,535 discloses thermoplastic elastomercompositions comprising thermoplastic olefin resins and olefin copolymerrubbers, prepared by dynamic vulcanization and wherein the rubbercomponent is vulcanized to the extent that it is essentially insolublein conventional rubber solvents. No details are given regarding adhesionproperties of these compositions, but it is known that unmodifiednon-polar thermoplastic elastomers generally do not adhere toengineering resins.

[0006] Efforts to improve the adhesive properties of thermoplasticelastomers have been made through the incorporation of functionalizedthermoplastic resins into the blends. One approach is described in U.S.Pat. No. 4,957,968 which discloses the addition of a functionalizedpolyolefin to improve adhesion to metals and polar polymers. U.S. PatNo. 5,843,577 describes the incorporation of copolymers of polyamide andfunctionalized polyolefin to improve adhesion to polyamides. U.S. Pat.No. 5,852,118 discloses the addition of block copolymers offunctionalized olefin, thermoplastic polyurethane, copolyester orcopolyamide, and an isocyanate.

[0007] However, the problem of achieving good adhesion of thermoplasticelastomers to polymer substrates, and particularly to polar engineeringthermoplastic substrates, either has not been overcome by theseapproaches or the techniques are too complex for practical application.

SUMMARY OF THE INVENTION

[0008] The present invention Is based on the discovery that athermoplastic elastomer composition having improved adhesion is providedby incorporating into the TPE a flexible block copolymer composed ofblocks of vinyl aromatic monomers and blocks of dienes and vinylaromatic monomers, and having a specific molecular structure. In detailthe present invention relates to a thermoplastic elastomer compositioncomprising

[0009] (a) from 25 to 90 weight percent of a thermoplastic elastomer,and

[0010] (b) from 10 to 75 weight percent of a block copolymer comprisingrigid blocks of vinyl aromatic monomers (S) having a glass transitiontemperature T_(g) of above 25° C. and non-rigid blocks of dienes andvinyl aromatic monomers (B/S), having a glass transition temperatureT_(g) of below 25% C. and containing at least the block structureS—B/S—S, wherein the diene content is less than 40 weight percent of thetotal block copolymer and the non-rigid blocks B/S amount to at least 50weight percent of the total block copolymer, based on the total weightof (a)+(b).

[0011] In a further embodiment the present invention relates to anadhesive composition comprising

[0012] (a) from 50 to 75 weight percent of a thermoplastic elastomercomprising a blend of polypropylene and dynamically vulcanizedethylene-propylene-nonconjugated diene terpolymer rubber, and

[0013] (b) from 25 to 50 weight percent of a block copolymer comprisingrigid blocks of styrene having a glass transition temperature Tg ofabove 25° C. and non-rigid blocks of 1,3-butadiene and styrene having aglass transition temperature Tg of below 25° C. and containing at leastthe block structure styrene-1,3-butadiene/styrene-styrene, wherein the1,3-butadiene content is less than 40 weight percent of the total blockcopolymer and the non-rigid blocks amount to at least 50 weight percentof the total block copolymer, based on the total weight of (a)+(b).

[0014] Additionally, the invention relates to a method for thepreparation of an adhesive composition, comprising the step of blendinga thermoplastic elastomer with a block copolymer comprising rigid blocksof vinyl aromatic monomers (S) having a glass transition temperature Tgof above 25° C. and non-rigid blocks of dienes and vinyl aromaticmonomers (B/S) having a glass transition temperature Tg of below 25° C.and containing at least the block structure S—B/S—S, wherein the dienecontent is less than 40 weight percent of the total block copolymer andthe non-rigid blocks B/S amount to at least 50 weight percent of thetotal block copolymer.

[0015] In a still further embodiment the present invention relates to ashaped article comprising at least one layer of a thermoplasticsubstrate which is at least partially in adherent contact with the withthe above composition.

[0016] Preferred embodiments become evident from the dependent claims.

[0017] The thermoplastic elastomer component (a) can be an olefinicthermoplastic elastomer wherein a thermoplastic olefin polymer and anolefin rubber are blended under conditions of heat and shear in thepresence of a curative to at least partially vulcanize (crosslink) therubber component to form a thermoplastic vulcanizate (TPV). Thethermoplastic elastomer component (a) can also be a styrenic blockcopolymer, or a mixture of olefinic and styrenic thermoplasticelastomers.

[0018] In a further embodiment of the invention thermoplasticpolyurethanes can also be incorporated into the compositions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Olefinic Thermoplastic Elastomer

[0020] Thermoplastic Olefin Polymer Component

[0021] Polyolefins suitable for use in the compositions of the inventioninclude thermoplastic, crystalline polyolefin homopolymers andcopolymers. They are desirably prepared from monoolefin monomers having2 to 7 carbon atoms, such as ethylene, propylene, 1-butene, isobutylene,1-pentene, 1-hexene, 1-octene, 3-methyl-1-pentene, 4-methyl-1-pentene,5-methyl-1-hexene, mixtures thereof and copolymers thereof with(meth)acrylates and/or vinyl acetates. Preferred, however, are monomershaving 3 to 6 carbon atoms, with propylene being most preferred. As usedin the specification and claims the term polypropylene includeshomopolymers of propylene as well as reactor and/or random copolymers ofpropylene which can contain 1 to 30 weight percent of ethylene and/or analpha-olefin comonomer of 4 to 16 carbon atoms, and mixtures thereof.The polypropylene can have different types of crystalline structure suchas isotactic or syndiotactic, and different degrees of crystallinityincluding materials with a high percentage of amorphous structure suchas the “elastic” polypropylenes. Further polyolefins which can be usedin the invention are high, low, linear-low and very low densitypolyethylenes, and copolymers of ethylene with (meth)acrylates and/orvinyl acetates.

[0022] The polyolefins mentioned above can be made using conventionalZiegler/Natta catalyst systems or by single site catalyst systems.Commercially available polyolefins may be used in the practice of theinvention.

[0023] The amount of thermoplastic polyolefin found to provide usefulthermoplastic elastomer compositions is generally from 8 to 90 weightpercent, with the proviso that the total amount of polyolefin andolefinic rubber is 35 weight percent based on the total weight of thethermoplastic polyolefin, olefin rubber and optional additives.Preferably, the thermoplastic polyolefin content will range from 10 to60 percent by weight.

[0024] Olefin Rubber Component

[0025] Suitable monoolefin copolymer rubbers include non-polar, rubberycopolymers of two or more alpha-monoolefins, preferably copolymerizedwith at least one polyene, usually a diene. Saturated monoolefincopolymer rubber, for example ethylene-propylene copolymer rubber (EPM)can be used. However, unsaturated monoolefin rubber such as EPDM rubberis more suitable. EPDM is a terpolymer of ethylene, propylene and anonconjugated diene. Satisfactory non-conjugated dienes include5-ethylidene-2-norbornene (ENB); 1,4-hexadiene; 5-methylene-2-norbornene(MNB); 1,6-octadiene; 5-methyl-1,4hexadiene; 3,7-dimethyl-1,6-octadiene;1,3-cyclopentadiene; 1,4-cyclohexadiene; dicyclopentadiene (DCPD); andvinyl norbornene (VNB).

[0026] Butyl rubbers are also useful in the thermoplastic elastomercompositions. As used in the specification and claims, the term butylrubber includes copolymers of an isoolefin and a conjugated monoolefin,terpolymers of an isoolefin with or without a conjugated monoolefin,divinyl aromatic monomers and the halogenated derivatives of suchcopolymers and terpolymers. Another suitable copolymer within the scopeof the olefin rubber of the present invention is a copolymer of a G₄₋₇isomonoolefin and a para-alkylstyrene, and preferably a halogenatedderivative thereof. The amount of halogen in the copolymer,predominantly In the para-alkylstyrene, is from 0.1 to 10 weight percentA preferred example is the brominated copolymer of isobutylene andpara-methylstyrene. Natural rubbers are also olefin rubbers suitable foruse in the thermoplastic elastomer composition.

[0027] The amount of olefin rubber in the thermoplastic elastomergenerally ranges from 70 to 10 weight percent, with the proviso that thetotal amount of thermoplastic polyolefin and olefin rubber is at least35 weight percent, based on the weight of the polyolefin, rubber andoptional additives. Preferably the olefin rubber content will be in therange of from 50 to 10 weight percent.

[0028] Additives

[0029] The thermoplastic elastomer may optionally contain reinforcingand non-reinforcing fillers, plasticizers, antioxidants, stabilizers,rubber processing oils, extender oils, lubricants, antiblocking agents,antistatic agents, waxes, foaming agents, pigments, flame retardants andother processing aids known in the rubber compounding art Such additivesmay comprise up to 65 weight percent, more preferably up to 50 weightpercent, of the total composition. Fillers and extenders which can beutilized include conventional inorganics such as calcium carbonate,clays, silica, talc, titanium dioxide, carbon black and the like. Therubber processing oils generally are paraffinic, napthenic or aromaticoils derived from petroleum fractions. The oils are selected from thoseordinarily used in conjunction with the specific rubber or rubbercomponent present in the composition.

[0030] Processing

[0031] The olefin rubber component of the olefinic thermoplasticelastomer is generally present as small, i.e. micro size, particleswithin a continuous polyolefin matrix, although a co-continuousmorphology or a phase inversion is also possible depending upon theamount of rubber relative to thermoplastic resin and the degree ofvulcanization, if any, of the rubber. Preferably, the rubber is at leastpartially vulcanized, and most preferably it is fully vulcanized(crosslinked).

[0032] The partial or full crosslinking can be achieved by adding anappropriate rubber curative to the blend of thermoplastic olefin polymerand olefin rubber, and vulcanizing the rubber to the desired degreeunder vulcanizing conditions. It is preferred that the rubber becrosslinked by the process of dynamic vulcanization. As used in thespecification and claims, the term dynamic vulcanization means avulcanization or crosslinking (curing) process wherein the rubber isvulcanized under conditions of shear at a temperature above the meltingpoint of the polyolefin component.

[0033] Those of ordinary skill in the art will appreciate theappropriate quantities and types of vulcanizing agents, and theconditions required to achieve the desired vulcanization. Any knowncrosslinking system can be used, so long as it is suitable under thevulcanization conditions for the elastomer component and it iscompatible with the thermoplastic olefin polymer component of thecomposition. Crosslinking (curing) agents include sulfur, sulfur donors,metal oxides, phenolic resin systems, maleimides, peroxide basedsystems, hydrosilylaton systems, high energy radiation and the like,both with and without accelerators and co-agents.

[0034] The terms fully vulcanized or completely vulcanized as usedherein mean that the olefin rubber component of the composition has beencrosslinked to a state in which the elastomeric properties of thecrosslinked rubber are similar to those of the rubber in itsconventional vulcanized state, apart from the thermoplastic elastomercomposition. The degree of crosslinking (or cure) of the rubber can alsobe expressed in terms of gel content, crosslink density or amount ofuncrosslinked rubber which is extractable by a rubber solvent. All ofthese descriptions are well known in the art.

[0035] Usually 5 to 20 parts by weight of the crosslinking agent orsystem are used per 100 parts by weight of the rubber component to bevulcanized.

[0036] Styrenic Thermoplastic Elastomer

[0037] Another thermoplastic elastomer useful in the invention is ablock copolymer of styrene/conjugated diene/styrene, with the conjugateddiene optionally being fully or partially hydrogenated, or mixturesthereof. Generally this block copolymer may contain 10 to 50 weight %,more preferably 25 to 35 weight %, of styrene and 90 to 50 weight %,more preferably 75 to 35 weight % of the conjugated diene, based on saidblock copolymer. Most preferred, however, is a block copolymer whichcontains 30 weight % of styrene and 70 weight % of the conjugated diene.The conjugated diene is selected from butadiene, isoprene or mixturesthereof. Specific block copolymers of the styrene/conjugateddiene/styrene type are SBS, SIS, SIBS, SEBS and SEPS block copolymers.These block copolymers are known in the art and are commerciallyavailable.

[0038] Optionally the block copolymer may be further compounded with apolyolefin or a common additive or mixtures thereof. Thus, the styrenicthermoplastic elastomer optionally further comprises up to 60 weight %of such polyolefin homopolymer or copolymer, or the additives ormixtures thereof, based on the total weight of the block copolymer andthe polyolefin and/or additives. Preferably, the styrenic thermoplasticelastomer comprises at least 10 weight % of the polyolefin. Thethermoplastic polyolefins are selected from those mentioned above incontext with the olefinic thermoplastic elastomers.

[0039] The thermoplastic elastomer component of the invention may alsobe blends of the olefinic thermoplastic elastomer (comprising thepolyolefin, rubber and optional additives) with the styrenicthermoplastic elastomer (comprising the block copolymer, optionalpolyolefin and/or additives). Preferred blends contain 5 to 95 weight %of olefinic thermoplastic elastomer and 95 to 5 weight % of styrenicthermoplastic elastomer respectively, based on the total weight of thethermoplastic elastomer component. These blends can be prepared bycommon blending processes known in the art.

[0040] The thermoplastic elastomer component of the compositionsgenerally is present in an amount from 25 to 90 weight %, based on thetotal weight of thermoplastic elastomer and flexible block copolymer.Preferably it is present from 25 to 85 weight %, and most preferablyfrom 50 to 75 weight %.

[0041] Thermoplastic Polyurethane

[0042] In a further embodiment of the invention, a thermoplasticpolyurethane (TPU) can be included in the adhesive composition. The TPUcomponent has no limitation with respect to its formulation other thanthe requirement that it be thermoplastic in nature, which means that itis prepared from substantially difunctional ingredients, i.e. organicdiisocyanates and components being substantially difunctional in activehydrogen containing groups. However, often minor proportions ofingredients with functionalities higher than two may be employed. Thisis particularly true when using extenders such as glycerol, trimethylolpropane, and the like. Any of the TPU materials known in the art can beemployed within the scope of the present invention.

[0043] The preferred TPU is a polymer prepared from a mixture comprisingat least one organic diisocyanate, at least one polymeric diol and atleast one difunctional extender. The TPU can be prepared by prepolymer,quasi-prepolymer or one-shot methods commonly used in the art.

[0044] The TPU component may be incorporated in amounts ranging from 10to 50 weight %, and preferably from 15 to 35 weight %, based on thetotal of thermoplastic elastomer, TPU and flexible block copolymer.

[0045] Flexible Block Copolymer

[0046] The composition of the Invention includes a flexible blockcopolymer component, which Is comprised of a block copolymer containingrigid blocks of vinyl aromatic monomers (S) and statistical non-rigidmid-blocks of diene/vinyl aromatic monomers (B/S). These blockcopolymers contain at least the block structure S—B/S—S. The glasstransition temperature (T_(g)) of block S is generally above 25° C. andthat of the block B/S is generally below 25° C. The B/S block iscomposed of 75 to 30 weight percent vinyl aromatic monomer and 25 to 70weight percent diene monomer. Particularly preferred flexible B/S blockshave a vinyl aromatic monomer content of 60 to 40 weight percent and adiene monomer content of 40 to 60 weight percent With respect to thetotal block copolymer component the diene content is less than 40 weightpercent, preferably 35 weight percent, and the portion of the non-rigidB/S blocks amounts to at least 50 weight percent, preferably 70 weightpercent. The block copolymer component has a low modulus and yieldstrength, with high elongation.

[0047] Suitable vinyl aromatic monomers include styrene,alkyl-substituted styrenes such as p-methylstyrene, vinyltoluene, aswell as mixtures of said monomers. The preferred monomer is styrene.Suitable diene monomers include 1,3-butadiene, isoprene, piperylene,phenylbutadiene, and mixtures of said monomers. The preferred monomer is1,3-butadiene. The conjugated diene monomer can also be fully orpartially hydrogenated.

[0048] The block copolymers useful in the thermoplastic elastomercompositions of the invention are known in the art, and are furtherdescribed in Canadian Pat. No. 2,193,264 and in International Pat.Applications WO 96/20248; WO 96/23823; WO 98/12240; and WO 99/46330.They are generally prepared by butyl lithium initiated sequentialanionic polymerization, but coupling of living S—B/S diblocks orbifunctional initiation are also known methods.

[0049] The amount of the block copolymer component in the composition ofthe invention generally ranges from 10 to 75 weight percent, based onthe total weight of the composition including the thermoplasticelastomer component, additives and the flexible block copolymercomponent. The preferred amount of flexible block copolymer ranges from15 to 75 weight percent, with 25 to 50 weight percent being mostpreferred.

EXAMPLES

[0050] The following general procedure was used in the preparation ofthermoplastic elastomers of the invention. The compositions wereprepared in a typical thermoplastic compounding twin screw extruder,although other conventional mixing devices such as Banbury mixers,Farrel continuous mixers and the like are also satisfactory. The pelletsof block copolymer were preblended with the thermoplastic elastomercomponent, and the blend was added to the extruder using aloss-in-weight belt feeder. The extrusion was set up to reach a melttemperature of at least 180° C. but not higher than 220° C. One extrudervent was used as a vacuum port to remove trace volatiles and to preventporosity in the extruded composition. The compositions were finishedinto spherical pellets using an underwater pelletizer After pelletizing,the compositions were molded into plaques for the determination ofphysical properties or were molded as described below for use in thepeel test.

[0051] The compositions of the invention are rubbery materials havingtensile set values of 50% or less, which meet the standards for rubberas defined by ASTM D1566. Preferred compositions have a Shore A hardnessof 65 or below and/or a tensile modulus (100%) of (270 psi)or lower.

[0052] The adhesive composition of the invention has unexpectedlyimproved adhesion to thermoplastic substrates such as terpolymers ofacrylonitrile, butadiene, and styrene (ABS), polycarbonate (PC), ABS/PCalloys and blends, polystyrene (PS), high impact polystyrene (HIPS),polyphenylene oxide (PPO), polymethyl methacrylate (PMMA), polybutyleneterephthalate (PBT), polyethylene terephthalate (PET), acrylonltrilestyrene acrylic (ASA), polypropylene, polyethylene and other olefinicpolymers, including blends and alloys of these polymers, as well asglass and mineral filled versions hereof. The compositions therefore canbe used in processes for making shaped articles by conventionalprocesses such as co-injection molding, co-extrusion molding, co-blowmolding (injection and extrusion), lamination, calendering, overmoldingby compression and injection, insert molding, and over-extrusion. Theshaped articles obtained by these processes are multilayer articlescomprising at least one layer of a polymer substrate and at least onelayer of the adhesive composition according to the invention. Theadhesive composition and the molded and shaped articles made therefromare useful in a variety of applications such as non-slip grips, softtouch labels and coatings, and consumer electronic, tool and applianceparts.

[0053] The following measurement methods were used In evaluating theexamples of the invention:

[0054] Tensile strength at break; tensile set; tensile modulus;elongation at break—ASTM D412 (ISO 37, type 2)

[0055] Shore hardness—ASTM D2240

[0056] Tear strength—ASTM D624.

[0057] Specific gravity—ASTM D792

[0058] Adhesion of the compositions of the invention was measured by apeel test modeled after ASTM D 1876, with the modification that a hardand soft substrate was used in place of two soft substrates. Also, sinceadhesion is obtained at the substrate Interface due to the inventivecomposition, no separate adhesive layer exists. For evaluation of insertmolding conditions the harder thermoplastic substrates were produced inan “L” shaped mold cavity, then were removed and allowed to cool toambient temperature. The shaped plastic profile was then inserted intoanother mold with a “T” shaped cavity, so as to take up one-half of thecavity. The molten composition of the invention was then injectionmolded onto the existing “L” to produce a “T-bar” article. Forevaluation of compression molding conditions the thermoplastic “L” isproduced as described, but is not removed from the mold. By eitherrotating the mold cavity to the next station or by using a sliding coreplate, the molded “L” is immediately made accessible in a “T” cavity andthe molten composition of the invention is injected. A standardtensiometer was then used to measure peel values for the “T-bars”, byplacing each tab of the upper “T” in separate grips. The grips were thenpulled apart at 180 degrees. The force to peel was plotted against thecrosshead travel which is also the peel length down the profile. Thecurve typically reached a peak and then descended to a plateau. Theplateau values were recorded as the adhesion, expressed as pounds perlinear inch (pli) Newton per meter (N/m)

[0059] The properties of compositions of the invention, and theiradhesion to ABS and PC substrates are set forth in Tables 1 and 2 TABLE1 Example No. - 1 2 3 4 5 6 7 8 9 10 Component (wt. %) SP8211 - 45W23770 100 SP9911 - 45W237 70 75 65 60 60 55 50 100 Styroflex BX6105 30 2535 30 40 45 50 30 Septon 4055 10 Properties Hardness (ShoreA) 52 51 5558 60 61 63 55 45 45 Tensile at break 580 540 610 930 920 1100 1210 610475 500 (psi)* Elongation at 590 590 640 710 740 770 780 540 500 450break (%) Tensile modulus 210 190 210 210 230 230 240 210 200 (100%(psi) Tensile set (%) 11 9 9 9 9 9 9 5 Adhesion (pli)** ABS (insert 1712 23 18 20 23 25 18 <1 <1 mold) PC (insert mold) 28 <1 <1 ABS(compression 26 mold) PC (compression 37 mold)

[0060] TABLE 2 Example No. - 11 12 13 14 15 16 Component (wt. %)SP8211 - 45W237 65 65 65 65 65 Styroflex BX6105 35 25 17.5 25 17.5 35Elastollan 1185 10 17.5 Elastollan C85A 10 17.5 Thermolast K - TC6AAZ 65Adhesion (pli)* ABS 19 16 7.5 20.5 17 8.5 PC 26.5 20 13 22.5 12 15

[0061] Adhesive compositions of the invention were prepared by blending65 weight % SP8211-55W237 thermoplastic elastomer with 35 weight %Styroflex BX6105 flexible block copolymer. Adhesion to various polymericsubstrates was tested by the insert molding technique described earlier.Results of the peel strength tests are set forth in Table 3. In thedescription of the adhesion mode, the notation “cohesive” means thatpeel or failure occurred in the body of either the substrate or thethermoplastic elastomer of the invention. The notation “adhesive” meansthat the peel or failure occurred at the interface between the substrateand the thermoplastic elastomer of the invention. TABLE 3 SubstrateAdhesion (pli)* Adhesion Mode Polycarbonate (PC) 29 CohesiveAcrylonitrile/butadiene/styrene (ABS) 21 Adhesive PC/ABS blend 29Cohesive PC - 30% glass filled 23 Cohesive Crystal polystyrene (PS) 29Cohesive High impact polystyrene (HIPS) 29 Cohesive Polymethylmethacrylate (PMMA) 19 Adhesive Acylic styrene acrylonitrile (ASA) 15Adhesive ASA/PC 17 Adhesive PC/polybutylene terephthalate (PBT) 21Adhesive Polyethylene terephthalate (PET) 17.5 Adhesive Polypropylene(PP) 25 Cohesive Polyphenylene oxide (PPO) 21 Cohesive

[0062] Abbreviations and product names used in the tables are defined asfollows:

[0063] SP8211 45W237—Santoprene® thermoplastic elastomer based onpolypropylene and vulcanized EPDM rubber (Advanced Elastomer Systems,L.P.)

[0064] SP821 1-55W237—Santoprene® thermoplastic elastomer based onpolypropylene and vulcanized EPDM rubber (Advanced Elastomer Systems,L.P.)

[0065] SP991 145W237—Santoprene® thermoplastic elastomer based onpolypropylene and vulcanized EPDM rubber (Advanced Elastomer Systems,L.P.)

[0066] Styroflex® BX6105—Flexible styrene-butadiene block copolymer(BASF Aktiengesellschaft)

[0067] Septon® 4055—Thermoplastic elastomer SEPS block copolymer(Kuraray Co., Ltd.)

[0068] Elastollan® 1185—Polyether based thermoplastic polyurethane (BASFCorp.)

[0069] Elastollan® C85—Polyester based thermoplastic polyurethane (BASFCorp.)

[0070] Thermolast K™—Compounded TPE based on SEBS (Gummiwerk Kraiburg)ABS—Acrylonitrile-butadiene-styrene terpolymer resin (Cycolac® 5600—GE)PC—Polycarbonate resin (GE)

1. An adhesive composition comprising (a) from 25 to 90 weight percentof a thermoplastic elastomer, and (b) from 10 to 75 weight percent of ablock copolymer comprising rigid blocks of vinyl aromatic monomers (S)having a glass transition temperature T_(g) of above 25° C. andnon-rigid blocks of dienes and vinyl aromatic monomers (B/S) having aglass transition temperature T_(g) of below 25% C. and containing atleast the block structure S—B/S—S, wherein the diene content is lessthan 40 weight percent of the total block copolymer and the non-rigidblocks B/S amount to at least 50 weight percent of the total blockcopolymer, based on the total weight of (a)+(b).
 2. The composition ofclaim 1 further comprising from 10 to 50 weight percent of athermoplastic polyurethane (c), based on the total weight of(a)+(b)+(c).
 3. The composition of claim 1 wherein said thermoplasticelastomer (a) comprises a blend of thermoplastic olefin homopolymer orcopolymer and olefin rubber, with optional additives.
 4. The compositionof claim 3 wherein said blend comprises a thermoplastic olefin polymerselected from the group consisting of polyethylene and polypropylene,and an olefin rubber selected from the group consisting ofethylene-propylene copolymer rubber and ethylene-propylene-nonconjugateddiene terpolymer rubber.
 5. The composition of claim 3 wherein saidolefin rubber is at least partially vulcanized.
 6. The composition ofclaim 1 wherein said thermoplastic elastomer (a) comprises a styrenicblock copolymer of styrene/conjugated diene/styrene.
 7. The compositionof claim 1 wherein said block copolymer (b) comprises rigid blocks ofstyrene and non-rigid blocks of 1, 3-butadiene and styrene.
 8. Thecomposition of claim 1 having a tensile set of 50% or less as determinedby ASTM D412.
 9. An adhesive composition comprising (a) from 50 to 75weight percent of a thermoplastic elastomer comprising a blend ofpolypropylene and dynamically vulcanizedethylene-propylene-nonconjugated diene terpolymer rubber, and (b) from25 to 50 weight percent of a block copolymer comprising rigid blocks ofstyrene having a glass transition temperature T_(g) of above 25° C. andnon-rigid blocks of 1,3-butadiene and styrene having a glass transitiontemperature T_(g) of below 25° C. and containing at least the blockstructure styrene-1,3-butadiene/styrene-styrene, wherein the1,3-butadiene content is less than 40 weight percent of the total blockcopolymer and the non-rigid blocks amount to at least 50 weight percentof the total block copolymer, based on the total weight of (a)+(b). 10.A shaped article comprising at least one layer of a thermoplasticsubstrate which is at least partially in adherent contact with thecomposition of claim
 1. 11. A method for the preparation of an adhesivecomposition, comprising the step of blending a thermoplastic elastomerwith a block copolymer comprising rigid blocks of vinyl aromaticmonomers (S) having a glass transition temperature T_(g) of above 25° C.and non-rigid blocks of dienes and vinyl aromatic monomers (B/S) havinga glass transition temperature Tg of below 25° C. and containing atleast the block structure S—B/S—S, wherein the diene content is lessthan 40 weight percent of the total block copolymer and the non-rigidblocks B/S amount to at least 50 weight percent of the total blockcopolymer.
 12. The method of claim 11 wherein said thermoplasticelastomer comprises a blend of thermoplastic olefin homopolymer orcopolymer and olefin rubber, with optional additives.
 13. The method ofclaim 11 wherein said thermoplastic elastomer comprises a thermoplasticolefin polymer selected from the group consisting of polyethylene andpolypropylene, and an olefin rubber selected from the group consistingof ethylene-propylene copolymer rubber andethylene-propylene-nonconjugated diene terpolymer rubber.
 14. The methodof claim 12 wherein the thermoplastic elastomer comprises athermoplastic olefin matrix having dispersed therein discrete particlesof olefin rubber which has been at least partially vulcanized by dynamicvulcanization.
 15. The method of claim 11 wherein said thermoplasticelastomer comprises a styrenic block copolymer of styrene/conjugateddiene/styrene.
 16. The method of claim 11 wherein said block copolymercomprises rigid blocks of styrene and non-rigid blocks of 1,3-butadieneand styrene.